As semiconductor wafer processing moves toward the flexibility of single wafer processing, the ability to accurately measure and control the process and wafer state parameters becomes increasingly important. One of the most important parameters that need to be accurately monitored and controlled is temperature. Currently, a majority of thermally activated single wafer processes such as rapid thermal processes rely on pyrometric temperature measurements. An important limitation of pyrometric temperature measurement in semiconductor processing is that there is generally a spectral overlap between radiation from the heating lamps used to heat the wafer and the radiation from the wafer used to measure temperature. Both radiation from the lamps and radiation from the wafer used to measure temperature mostly overlap in the quartz transmission band. For instance, tungsten-halogen lamp radiation spectrum usually extends from less than 1 .mu.m wavelength to less than 4 .mu.m which is mostly in the transmission band (200 um to 3.5 .mu.m) of thick quartz windows used in rapid thermal processing (RTP) systems. The pyrometer cannot distinguish between the radiation from the two (wafer and lamp) sources, and thus error is introduced into the temperature measurement. The error is particularly significant at lower wafer temperatures (e.g., at below 500.degree. C.) during the temperature ramp-up and low-temperature processing where thermal radiation from the wafer is relatively small compared to lamp radiation. While lamp radiation introduces error at all temperatures up to the highest processing temperatures used in semiconductor processing, the effect of the radiation is particularly severe at lower temperatures.